Biological information detector and biological information measuring device

ABSTRACT

A biological information detector is adapted to be attached to a user&#39;s body, and includes a light-emitting part, a reflecting part, a light-receiving part and a processing unit. The light-emitting part is configured to emit light toward the user&#39;s body. The reflecting part is disposed in a periphery of the light-emitting part to reflect at least a part of the light emitted by the light-emitting part toward the user&#39;s body. The light-receiving part is configured to receive light reflected at the user&#39;s body to produce a light reception signal. The processing unit is configured to process the light reception signal to produce biological information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 12/973,259 filed on Dec. 20, 2010. This application claims priorityto Japanese Application No. 2010-000453 filed on Jan. 5, 2010. Theentire disclosures of U.S. application Ser. No. 12/973,259 and JapaneseApplication No. 2010-000453 are hereby incorporated herein by reference.

BACKGROUND

1. Technological Field

The present invention relates to a biological information detector and abiological information measuring device and similar devices.

2. Background Technology

A biological information measuring device measures human biologicalinformation such as, for example, pulse rate, blood oxygen saturationlevel, body temperature, or heart rate, and an example of a biologicalinformation measuring device is a pulse rate monitor for measuring thepulse rate. Also, a biological information measuring device such as apulse rate monitor may be installed in a clock, a mobile phone, a pager,a PC, or another electrical device, or may be combined with theelectrical device. The biological information measuring device has abiological information detector for detecting biological information,and the biological information detector includes a light-emitting partfor emitting light towards a detection site of a test subject (e.g. auser), and a light-receiving part for receiving light having biologicalinformation from the detection site.

In Patent Citation 1, there is disclosed a pulse rate monitor (or in abroader sense, a biological information measuring device). Alight-receiving part (e.g. a light-receiving part 12 in FIG. 16 ofPatent Citation 1) of the pulse rate monitor receives light reflected ata detection site (e.g. dotted line in FIG. 16 of Patent Citation 1) viaa diffusion reflection plane (e.g. reflecting part 131 in FIG. 16 ofPatent Citation 1). In an optical probe 1 in Patent Citation 1 (or in abroader sense, a biological information detector), a light-emitting part11 and the light-receiving part 12 overlap in plan view, and the size ofthe optical probe is reduced.

PRIOR ART REFERENCE

-   Patent Citation 1: JP-A 2004-337605 is an example of related art.

SUMMARY

In the optical probe 1 of Patent Citation 1, in an instance in whichthere is a significant level of noise arising from to e.g. externallight, or under similar circumstances, the detection accuracy of thebiological information detector is poor.

According to several modes of the present invention, it is possible toprovide a biological information detector and a biological informationmeasuring device in which the detection accuracy or the measurementaccuracy can be improved.

A biological information detector according to one aspect is adapted tobe attached to a user's body, and includes a light-emitting part, areflecting part, a light-receiving part and a processing unit. Thelight-emitting part is configured to emit light toward the user's body.The reflecting part is disposed in a periphery of the light-emittingpart to reflect at least a part of the light emitted by thelight-emitting part toward the user's body. The light-receiving part isconfigured to receive light reflected at the user's body to produce alight reception signal. The processing unit is configured to process thelight reception signal to produce biological information

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a configuration of a biological informationdetector according to a present embodiment;

FIG. 2 includes diagrams (A), (B), and (C) that are examples ofconfigurations of a first reflecting part;

FIG. 3 includes diagrams (A) and (B) that are examples of the outerappearance of the first reflecting part and a light-emitting part;

FIG. 4 is another example of a configuration of the biologicalinformation detector according to the present embodiment;

FIG. 5 is an example of an outer appearance of a light-receiving part;

FIG. 6 is a schematic diagram showing a setting position of the secondreflecting part;

FIG. 7 is a diagram showing a relationship between the setting positionof the second reflecting part and the amount of light received at thelight-receiving part;

FIG. 8 includes diagrams (A) and (B) that are examples of the outerappearance of a biological information measuring device containing thebiological information detector; and

FIG. 9 is an example of a configuration of the biological informationmeasuring device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A description shall now be given for the present embodiment. The presentembodiment described below is not intended to unduly limit the scope ofthe Claims of the present embodiment. Not every configuration describedin the present embodiment is necessarily an indispensible constituentfeature of the present invention.

1. Biological Information Detector

FIG. 1 shows an example of a configuration of a biological informationdetector according to the present embodiment. As shown in FIG. 1, thebiological information detector contains a light-emitting part 14, afirst reflecting part 12, a light-receiving part 16, and a secondreflecting part 18. The light-emitting part 14 generates a first lightR1 directed at a detection site O of a test subject (e.g. a user), and asecond light R2 directed at a direction other than a direction of thedetection site O (i.e., directed at the first reflecting part 12). Thefirst reflecting part 12 reflects the second light R2 and directs thesecond light R2 towards the detection site O. The light-receiving part16 receives lights R1′, R2′ (i.e., reflected lights), having biologicalinformation, the lights R1′, R2′ produced by each of the first light R1and the second light R2 being reflected at the detection site O. Thesecond reflecting part 18 reflects the lights R1′, R2′ having biologicalinformation from the detection site O (i.e. the reflected lights) anddirects the lights R1′, R2′ towards the light-receiving part 16. Thepresence of the first reflecting part 12 causes the light second lightR2, that does not directly reach the detection site O of the testsubject (i.e., the user), to reach the detection site O. In other words,the amount of light reaching the detection site O via the firstreflecting part 12 increases, and the efficiency of the light-emittingpart 14 increases. Therefore, the detection accuracy (i.e., thesignal-to-noise ratio) of the biological information detector increases.

In Patent Citation 1, there is disclosed a configuration correspondingto the second reflecting part 18 (i.e., a reflecting part 131 in FIG. 16of Patent Citation 1). Specifically, the light-receiving part 12 in FIG.16 of Patent Citation 1 receives light reflected at a detection site viathe reflecting part 131. However, in Patent Citation 1, a configurationcorresponding to the first reflecting part 12 is not disclosed. In otherwords, at the time of filing, those skilled in the art had not beenaware of the issue of increasing the efficiency of the light-emittingpart 11 in FIG. 16 in Patent Citation 1.

In the example shown in FIG. 1, the detection site O (e.g. a bloodvessel) is within the test subject. As shown in FIG. 1, thelight-emitting part 14 may have a first light-emitting surface 14A foremitting the first light R1, the first light-emitting surface 14A facingthe detection site O. The first light R1 travels into the test subjectand diffuses or scatters at the epidermis, the dermis, and thesubcutaneous tissue. The first light R1 then reaches the detection siteO, and is reflected at the detection site O. The reflected light R1′reflected at the detection site O diffuses or scatters at thesubcutaneous tissue, the dermis, and the epidermis, and travels to thesecond reflecting part 18. The first light R1 is also partially absorbedat the blood vessel (or in a broader sense, the detection site O).Therefore, due to an effect of a pulse, the rate of absorption at theblood vessel varies, and the amount of the reflected light R1′ reflectedat the detection site O also varies. Biological information (e.g. pulserate) is thus reflected in the reflected light R1′ reflected at thedetection site O.

In the example shown in FIG. 1, the light-emitting part 14 may also havea second light-emitting surface 14B for emitting the second light R2,the second light-emitting surface 14B being a side surface of the firstlight-emitting surface 14A. In such an instance, the first reflectingpart 12 may have a wall part surrounding the second light-emittingsurface 14B, and the wall part may have a first reflecting surface(corresponding to label 12-2 shown in FIGS. 2(A) through 2(C)) capableof reflecting the second light R2 towards the detection site O. Thesecond light R2 is not necessarily limited to that emitted from thesecond light-emitting surface 14B. Specifically, the first reflectingsurface (label 12-2 shown in FIGS. 2(A) through 2(C)) reflects lightother than light travelling directly from the light-emitting part 14 tothe detection site O (i.e., the second light R2) and directs the secondlight R2 towards the detection site O.

The second light R2 also travels into the test subject, and thereflected light R2′ reflected at the detection site O travels towardsthe second reflecting part 18. Biological information (i.e., the pulserate) is also reflected in the reflected light R2′ reflected at thedetection site O. In the example shown in FIG. 1, the first light R1 ispartially reflected at a surface SA of the test subject (e.g. a skinsurface). In an instance in which the detection site O is within thetest subject, biological information (i.e., the pulse rate) is notreflected in reflected light R1″ reflected at the surface SA of the testsubject (i.e., a directly reflected light).

The wall part of the first reflecting part 12 may further have a secondreflecting surface (corresponding to 12-3 in FIGS. 2(A) and 2(C)) forreflecting light not having biological information (i.e., invalid light;noise) reflected at the surface of the test subject, thereby minimizingincidence of light not having biological information onto thelight-receiving part.

Examples of configurations of the biological information detector arenot limited by that shown in FIG. 1, and the shape, or a similarattribute, of a part of the example of configuration (e.g. the firstreflecting part 12) may be modified. The biological information may alsobe blood oxygen saturation level, body temperature, heart rate, or asimilar variable; and the detection site O may be positioned at thesurface SA of the test subject. In the example shown in FIG. 1, each ofthe first light R1 and the second light R2 is shown by a single line;however, in reality, the light-emitting part 14 emits many light beamsin a variety of directions.

The light-emitting part 14 is, for example, an LED. The light emitted bythe LED has a maximum intensity (or in a broader sense, a peakintensity) within a wavelength range of e.g. 425 nm to 625 nm, and ise.g. green in color. The thickness of the light-emitting part 14 is e.g.20 μm to 1000 μm. The light-receiving part 16 is e.g. a photodiode, andcan generally be formed by a silicon photodiode. The thickness of thelight-receiving part 16 is e.g. 20 μm to 1000 μm. The silicon photodiodehas a maximum sensitivity (or in a broader sense, a peak sensitivity)for received light having a wavelength within a range of e.g. 800 nm to1000 nm. Ideally, the light-receiving part 16 is formed by a galliumarsenide phosphide photodiode, and the gallium arsenide phosphidephotodiode has a maximum sensitivity (or in a broader sense, a peaksensitivity) for received light having a wavelength within a range ofe.g. 550 nm to 650 nm. Since biological substances (water or hemoglobin)readily allow transmission of infrared light within a wavelength rangeof 700 nm to 1100 nm, the light-receiving part 16 formed by the galliumarsenide phosphide photodiode is more capable of reducing noisecomponents arising from external light than the light-receiving part 16formed by the silicon photodiode.

FIGS. 2(A), 2(B), and 2(C) respectively show an example of aconfiguration of the first reflecting part 12 shown in FIG. 1. As shownin FIG. 2(A), the first reflecting part 12 may have a support part 12-1for supporting the light-emitting part 14, and an inner wall surface12-2 and a top surface 12-3 of the wall part surrounding the secondlight-emitting surface 14B of the light-emitting part 14. In FIGS. 2(A)through 2(C), the light-emitting part 14 is omitted. In the exampleshown in FIG. 2(A), the first reflecting part 12 is capable ofreflecting the second light R2 towards the detection site O off theinner wall surface 12-2 (see FIG. 1), and has the first reflectingsurface on the inner wall surface 12-2. The thickness of the supportpart 12-1 is e.g. 50 μm to 1000 μm, and the thickness of the top surface12-3 is e.g. 100 μm to 1000 μm. The first reflecting part 12 may notnecessarily have the support part 12-1, and the light-emitting part 14may be supported by a part other than the first reflecting part 12.

In the example shown in FIG. 2(A), the inner wall surface 12-2 has aninclined surface (12-2) which, with increasing distance in a widthdirection (i.e., a first direction) from a center of the firstreflecting part 12, inclines towards the detection site O in a heightdirection (i.e., a direction that is orthogonal with the firstdirection), in cross-section view. The inclined surface (12-2) in FIG.2(A) is formed by, in cross-section view, an inclined plane, but mayalso be a curved surface shown in e.g. FIG. 2(C), or a similar inclinedsurface. The inner wall surface 12-2 may also be formed as a pluralityof inclined flat surfaces whose angle of inclination vary from oneanother, or by a curved surface having a plurality of curvatures. In aninstance in which the inner wall surface 12-2 of the first reflectingpart 12 has an inclined surface, the inner wall surface 12-2 of thefirst reflecting part 12 is capable of reflecting the second light R2towards the detection site O. In other words, the inclined surface onthe inner wall surface 12-2 of the first reflecting part 12 can be saidto be the first reflecting surface for improving the directivity of thelight-emitting part 14. In such an instance, the amount of lightreaching the detection site O increases further. The top surface 12-3shown in FIGS. 2(A) and 2(C) may be omitted as shown, for example, inFIG. 2(B). In an instance in which the first reflecting part 12 has thetop surface 12-3, the reflected light R1″ reflected at the surface SA ofthe test subject (i.e., the directly reflected light) can be reflectedtowards the detection site O or surroundings thereof, and the reflectedlight R1″ is deterred from reaching the light-receiving part 16 (seeFIG. 1). Specifically, the top surface 12-3 shown in FIGS. 2(A) and 2(C)can be said to be the second reflecting surface for reflecting thedirectly reflected light (or in a broader sense, noise) that wouldotherwise reach the second reflecting part 18 and the light-receivingpart 16, and reducing noise. In FIGS. 2(A) through 2(C), a rangeindicated by label 12-4 function as a mirror surface part.

In the example shown in FIG. 1, the first reflecting part 12 may projecttowards the detection site O by e.g. a predetermined height Δh1 (whereΔh1 is e.g. 50 μm to 950 μm) in relation to a surface of thelight-emitting part 14 that determines the shortest distance relative tothe surface SA of the test subject (e.g. the first light-emittingsurface 14A). In other words, a spacing between the first reflectingpart 12 and the surface SA of the test subject (e.g. Δh2=βh0−Δh1, whereΔh2 is 200 μm to 1200 μm) may be smaller than a spacing that representsthe shortest distance between the light-receiving part 14 and thesurface SA of the test subject (e.g. Δh0=Δh1+Δh2). Therefore, in thefirst reflecting part 12, the presence of e.g. a projection Δh1 from thelight-emitting part 14 makes it possible to increase the area of thefirst reflecting surface (12-2) and increase the amount of lightreaching the detection site O. Also, with regards to the light reflectedat the detection site O, the presence of a space Δh2 between the firstreflecting part 12 and the surface SA of the test subject makes itpossible to obtain a light path for the light to reach the secondreflecting part 18 from the detection site O. Also, in an instance inwhich the first reflecting part 12 has the second reflecting surface(12-3), adjusting Δh1 and Δh2 allows the amount of light havingbiological information (i.e., valid light) and light not havingbiological information (i.e., invalid light: noise) incident on thelight-receiving part 16 to be respectively adjusted, thereby making itpossible to further improve the S/N.

FIGS. 3(A) and 3(B) respectively show an example of an outer appearanceof the first reflecting part 12 and the light-emitting part 14 of FIG. 1in plan view. In the example shown in FIG. 3(A), in plan view (whenviewed from e.g. towards the detection site O shown in FIG. 1), an outercircumference of the first reflecting part 12 is circular, where thediameter of the circle is e.g. 200 μm to 11,000 μm. In the example shownin FIG. 3(A), the wall part (12-2) of the first reflecting part 12surround the light-emitting part 14 (see FIGS. 1 and 2(A)). The outercircumference of the first reflecting part 12 may also be aquadrilateral (or specifically, a square) in plan view as shown e.g. inFIG. 3(B). Also, in the examples shown in FIGS. 3(A) and 3(B), in planview (when viewed from e.g. towards the detection site O shown in FIG.1), the outer circumference of the light-emitting part 14 is aquadrilateral (or specifically, a square), where the length of one sideof the square is e.g. 100 μm to 10,000 μm. The outer circumference ofthe light-emitting part 14 may also be circular.

The first reflecting part 12 is made of metal whose surface is subjectedto mirror surface finishing, and thereby has a reflective structure (orspecifically, a mirror reflection structure). The first reflecting part12 may also be formed from e.g. a resin whose surface is subjected tomirror surface finishing. Specifically, for example, a base metalforming a base of the first reflecting part 12 is readied, and a surfaceof the base metal is then e.g. subjected to plating. Alternatively, amold of the first reflecting part 12 (not shown) is filled with athermoplastic resin, molding is performed, and a metal film, forexample, is then deposited by vapor deposition on a surface of the mold.

In the examples shown in FIGS. 3(A) and 3(B), in plan view (when viewedfrom e.g. towards the detection site O shown in FIG. 1), a region of thefirst reflecting part 12 other than that directly supporting thelight-emitting part 14 (the inner wall surface 12-2 and the top surface12-3, and a part of the support part 12-1) is exposed. The exposedregion is shown as a mirror surface part 12-4 in FIG. 2(A). Although inthe example shown in FIG. 2(A), a dotted line representing the mirrorsurface part 12-4 is shown within the first reflecting part 12, themirror surface part 12-4 is actually formed on a surface of the firstreflecting part 12.

In the examples shown in FIGS. 2(A), 2(B), and 2(C), the mirror surfacepart 12-4 preferably has a high reflectivity. The reflectivity of themirror surface part 12-4 is e.g. 80% to 90% or higher. It is possiblefor the mirror surface part 12-4 to be formed only on the inclinedsurface of the inner wall surface 12-2. In an instance in which themirror surface part 12-4 is formed not only on the inclined surface ofthe inner wall surface 12-2 but also on the support part 12-1, thedirectivity of the light-emitting part 14 increases further. In aninstance in which the mirror surface part 12-4 is formed on the topsurface 12-3, the first reflecting part 12 is capable of reflecting thereflected light R1″, which has been reflected in the surface SA of thetest subject (i.e., the directly reflected light; invalid light),towards the detection site O or the surroundings thereof, as shown e.g.on FIG. 1, and the reflected light R1″ is deterred from reaching thesecond reflecting part 18 and the light-receiving part 16. Since thedirectivity of the light-emitting part 14 increases and the directlyreflected light (or in a broader sense, noise) decreases, the detectionaccuracy of the biological information detector increases.

FIG. 4 shows another example of a configuration of the biologicalinformation detector according to the present embodiment. As shown inFIG. 4, the biological information detector may further comprise asubstrate 41 having a first surface (e.g. a front surface) and a secondsurface that is opposite the first surface (e.g. a reverse surface).Structures that are identical to those in the example described aboveare affixed with the same numerals, and a description of the structureswill be omitted. In the example shown in FIG. 4, the light-receivingpart 16 is positioned on the first surface, and the first reflectingpart 12 is positioned on the second surface. When, in cross-sectionview, W1 is a maximum value for the length of the first reflecting part12 in a direction parallel to the first surface, and W2 is a maximumvalue for the length of the light-receiving part 16 in the samedirection, an equation W1≦W2 is satisfied.

The substrate 41 is formed of e.g. a transparent material (e.g.polyimide) and allows transmission of the reflected light R1′ producedby the first light R1 emitted at the detection site O, and other light.The maximum value W1 for the length of the first reflecting part 12 ismade equal to or less than the maximum value W2 for the length of thelight-receiving part 16, thereby making it possible to increase theamount of light reaching the second reflecting part 18. In other words,the maximum value W1 for the length of the first reflecting part 12 canbe set so that the first reflecting part 12 does not block or reflectthe reflected light R1' reflected at the detection site O. The thicknessof the substrate 41 is e.g. 10 μm to 1000 μm. Wiring for thelight-emitting part 14 and wiring for the light-receiving part 16 may beformed on the substrate 41. The substrate 41 is e.g. a printed circuitboard; however, a printed circuit board is not generally formed from atransparent material, as with the substrate 15 of Patent Citation 1.Specifically, the inventors purposefully used a configuration in whichthe printed circuit board is formed from a material that is transparentat least with respect to the emission wavelength of the light-emittingpart 14.

In the example shown in FIG. 4, the second light R2 emitted at thedetection site O via the first reflecting part 12, the reflected lightR2′ reflected at the detection site O, and the reflected light R1″reflected at the surface SA of the test subject (i.e., the directlyreflected light) are omitted (refer to FIG. 1). Those skilled in the artshould be readily able to understand the path of the second light R2 andthe accurate path of the first light R1.

As shown in FIG. 4, the biological information detector may furthercontain a protecting part 49 for protecting the first reflecting part 12and the light-emitting part 14. The protecting part 49 is formed frome.g. a transparent material (e.g. glass), and allows transmission of thefirst light R1 emitted at the detection site O, the reflected light R1′produced by the first light R1 being reflected, and other light. Theprotecting part 49 also makes it possible to ensure that there is a gapbetween the first reflecting part 12 and the detection site O (e.g.Δh2). There also exists a gap between the first reflecting part 12 andthe protecting part 49 (e.g. Δh2′). The thickness of the protecting part49 is e.g. 1 μm to 1000 μm.

The substrate 41 is held between the second reflecting part 18 and theprotecting part 49; the light-receiving part 16 is placed on thesubstrate 41 towards the second reflecting part 18 (or specifically, onthe first surface of the substrate 41); and the light-emitting part 14is placed on the substrate 41 towards the protecting part 49 (orspecifically, on the second surface of the 41). Since the substrate 41is held between the second reflecting part 18 and the protecting part49, even when the light-emitting part 14 and the light-receiving part 16are positioned on the substrate 41, there is no need to separatelyprovide a mechanism for supporting the substrate 41 itself, and thenumber of components is smaller. Also, since the substrate 41 is formedfrom a material that is transparent with respect to the emissionfrequency, the substrate 41 can be disposed on a light path from thelight-emitting part 14 to the light-receiving part 16, and there is noneed to accommodate the substrate 41 at a position away from the lightpath, such as within the second reflecting part 18. A biologicalinformation detector that can be readily assembled can thus be provided.

FIG. 5 shows an example of an outer appearance of the light-receivingpart 16 in FIG. 4. In the example shown in FIG. 5, in plan view (e.g.when viewed from a side towards the second reflecting part 18 in FIG.4), an outer circumference of the light-receiving part 16 is aquadrilateral (or specifically, a square), and one side of the square ise.g. 100 μm to 10,000 μm. An outer circumference of the first reflectingpart 12 is, in plan view (e.g. when viewed from a side towards thesecond reflecting part 18 in FIG. 4), circular. The outer circumferenceof the first reflecting part 12 may instead be a quadrilateral (orspecifically, a square), as in the example shown in FIG. 3(B). The outercircumference of the light-receiving part 16 may also be circular.

In the example shown in FIG. 5, as shown by line segment A-A′, when W1is a maximum value for the length of the first reflecting part 12 and W2is a maximum value for the length of the light-receiving part 16, anequation W1≦W2 is satisfied. A cross-section view along the line segmentA-A′ in FIG. 5 corresponds to FIG. 4. A cross-section view along linesegment B-B′ in FIG. 5 resembles FIG. 1, and the maximum value W1 of thelength of the first reflecting part 12 is larger than a minimum value ofthe length of the light-receiving part 16. Although the maximum value WIof the length of the first reflecting part 12 may be set so as to beequal to or smaller than the minimum value of the length of thelight-receiving part 16, the efficiency of the first reflecting part 12(or, in a broader sense, the efficiency of the light-emitting part 14)would decrease. In the example shown in FIG. 5, the maximum value W1 ofthe length of the first reflecting part 12 is set to be equal or smallerthan the maximum value W2 of the length of the light-receiving part 16,and the maximum value W1 of the length of the first reflecting part 12is set to be larger than the minimum value of the length of thelight-receiving part 16, so that the efficiency of the light-emittingpart 14 can be maintained without blocking or reflecting the reflectedlight R1′.

FIG. 6 is a schematic diagram showing a setting position of the secondreflecting part 18 in FIG. 1 or 4. The reflecting surface of the secondreflecting part 18 may be formed as e.g. a spherical surface (or in abroader sense, a dome surface), so that the reflected light R1′,produced by the first light R1 being reflected at the detection site O,is reflected towards the light-receiving part 16. As shown in FIG. 6, incross-section view, the reflecting surface of the second reflecting part18 is an arc. The radius of the arc is e.g. 1000 μm to 15,000 μm. Acenter C of the arc that defines the spherical surface is located withinthe test subject. In an instance in which the detection site O islocated within the test subject, the reflected light R1″ reflected atthe surface SA of the test subject is an invalid light not havingbiological information. The inventors identified that in an instance inwhich the reflecting surface of the second reflecting part 18 is formedby a spherical surface and the center C of the arc that defines thespherical surface, the second reflecting part 18 minimizes reflectedlight reflected at the surface SA of the test subject (or in a broadersense, noise). In FIG. 6, the distance between the light-receivingsurface of the light-receiving part 16 and the center C of the arc thatdefines the spherical surface is represented by Δh.

The reflecting surface of the second reflecting part 18 may also beformed by a parabolic surface (or in a broader sense, a dome surface)instead of the spherical surface. As shown in FIG. 6, in cross-sectionview, the reflecting surface of the second reflecting part 18 is an arc,but may be a parabolic line instead of an arc. If the reflecting surfaceof the second reflecting part 18 is a parabolic surface, the focus ofthe parabolic line defining the parabolic surface is shown in FIG. 6 bythe letter F. The focus F of the parabolic line defining the parabolicsurface is located towards the test subject relative to thelight-receiving surface of the light-receiving part 16. Light thattravels perpendicular to the surface SA of the test subject reflects atthe reflecting surface of the second reflecting part 18 (i.e., theparabolic surface) and collects at the focus F of the parabolic linedefining the parabolic surface. Therefore, the focus F being located soas to not coincide with the light-receiving surface of thelight-receiving part 16 results in a greater likelihood of light havinga path that is nearly perpendicular to the surface SA of the testsubject (e.g. the reflected light R1′ produced by reflection of thefirst light R1; valid light) collecting on the light-receiving surfaceof the light-receiving part 16.

The second reflecting part 18 is formed from e.g. a resin, whose surface(i.e., the reflecting surface facing the light-receiving part 16) issubjected to mirror surface finishing, and thereby has a reflectivestructure (or specifically, a mirror reflection structure). In otherwords, the second reflecting part 18 is capable of causing mirrorreflection of light without causing diffuse reflection of light. In aninstance in which the second reflecting part 18 has a mirror reflectionstructure, the second reflecting part 18 is also capable of not causingthe reflected light R1″ (i.e., the directly reflected light) to reflecttowards the light-receiving part 16, where the reflected light R1″produced by reflection of the first light R1 has a reflection angle thatis different to that of the reflected light R1′ produced by reflectionof the first light R1. In such an instance, the detection accuracy ofthe biological information detector further increases. As shown in FIG.6, since the reflected light R1′ produced by reflection of the firstlight R1 originates from the detection site O that is within the testsubject, the reflection angle of the reflected light R1′ produced byreflection of the first light R1 (i.e., a reflection angle relative to astraight line perpendicular to the surface SA of the test subject) isgenerally small. Meanwhile, since the reflected light R1″ produced byreflection of the first light R1 originates from the surface SA of thetest subject, the reflection angle of the reflected light R1″ producedby reflection of the first light R1 is generally large.

In FIG. 16 of Patent Citation 1, there is disclosed a reflecting part131, and according to paragraphs [0046], [0059], and [0077] in PatentCitation 1, the reflecting part 131 has a diffuse reflection structure,and the reflectivity is increased to increase the efficiency of thefirst reflecting part 12. However, at the time of filing, it had notbeen recognized by those skilled in the art that in the reflecting part131 according to Patent Citation 1, directly reflected light (or in abroader sense, noise) is also reflected towards the first reflectingpart 12. In other words, the inventors identified that reducing a noisecomponent arising from the directly reflected light from a lightreception signal increases the efficiency of the light-receiving part.Specifically, the inventors identified that the detection accuracy ofthe biological information detector is further increased in an instancein which the second reflecting part 18 has a mirror reflectionstructure.

FIG. 7 is a diagram showing a relationship between the setting positionof the second reflecting part 18 and the amount of light received at thelight-receiving part 16 in FIG. 6. As shown in FIG. 7, with increasingdistance Δh between the light-receiving surface of the light-receivingpart 16 and the center C of the arc defining the spherical surface, theamount of directly reflected light reflected at the surface SA of thetest subject (or, in a broader sense, noise corresponding to thereflected light R1″, for example) decreases, while light reflected atthe detection site O (or, in a broader sense, biological informationcorresponding to reflected light R1′, for example) increases and thendecreases. The position of the Ah can accordingly be optimized. In aninstance in which the reflecting surface of the second reflecting part18 is a parabolic surface, the distance between the light-receiving partof the light-receiving part 16 and the focus F of the parabolic linedefining the parabolic surface can also be optimized.

2. Biological Information Measuring Device

FIGS. 8(A) and 8(B) are examples of outer appearances of a biologicalinformation measuring device containing the biological informationdetector such as that shown in FIG. 1. As shown in FIG. 8(A), thebiological information detector shown in FIG. 1, for example, mayfurther contain a wristband 80 capable of attaching the biologicalinformation detector to an arm (or specifically, a wrist) of the testsubject (i.e., the user). In the example shown in FIG. 8(A), thebiological information is the pulse rate indicated by e.g. “72.” Thebiological information detector is installed in a watch showing the time(e.g. “8:15 am”). As shown in FIG. 8(B), an opening part is provided toa back cover of the watch, and the protecting part 49 shown in FIG. 4,for example, is exposed in the opening part. In the example shown inFIG. 8(B), the second reflecting part 18 and the light-receiving part 16are installed in a watch. In the example shown in FIG. 8(B), the firstreflecting part 12, the light-emitting part 14, the wristband 80, andother components are omitted.

FIG. 9 is an example of a configuration of the biological informationmeasuring device. The biological information measuring device includesthe biological information detector as shown e.g. in FIG. 1, and abiological information measuring part for measuring biologicalinformation from a light reception signal generated at thelight-receiving part 16 of the biological information detector. As shownin FIG. 9, the biological information detector may have a light-emittingpart 14 and a control circuit 91 for controlling the light-emitting part14. The biological information detector may further have anamplification circuit 92 for amplifying the light reception signal fromthe light-receiving part 16. The biological information measuring partmay have an A/D conversion circuit 93 for performing A/D conversion ofthe light reception signal from the light-receiving part 16, and a pulserate computation circuit 94 for computationally obtaining the pulserate. The biological information measuring part may further have adisplay part 95 for displaying the pulse rate.

The biological information detector may have an acceleration detectingpart 96, and the biological information measuring part may further havean A/D conversion circuit 97 for performing A/D conversion of a lightreception signal from the acceleration detecting part 96 and a digitalsignal processing circuit 98 for processing a digital signal. Theconfiguration of the biological information measuring device is notlimited to that shown in FIG. 9. The pulse rate computation circuit 94in FIG. 9 may be e.g. an MPU (i.e., a micro processing unit) of anelectronic device installed with the biological information detector.

The control circuit 91 in FIG. 9 drives the light-emitting part 14. Thecontrol circuit 91 is e.g. a constant current circuit, delivers apredetermined voltage (e.g. 6 V) to the light-emitting part 14 via aprotective resistance, and maintains a current flowing to thelight-emitting part 14 at a predetermined value (e.g. 2 mA). The controlcircuit 91 is capable of driving the light-emitting part 14 in anintermittent manner (e.g. at 128 Hz) in order to reduce consumptioncurrent. The control circuit 91 is formed on e.g. a motherboard, andwiring between the control circuit 91 and the light-emitting part 14 isformed e.g. on the substrate 41 shown in FIG. 4.

The amplification circuit 92 shown in FIG. 9 is capable of removing a DCcomponent from the light reception signal (i.e., an electrical current)generated in the light-receiving part 16, extracting only an ACcomponent, amplifying the AC component, and generating an AC signal. Theamplification circuit 92 removes the DC component at or below apredetermined wavelength using e.g. a high-pass filter, and buffers theAC component using e.g. an operational amplifier. The light receptionsignal contains a pulsating component and a body movement component. Theamplification circuit 92 and the control circuit 91 are capable offeeding a power supply voltage for operating the light-receiving part 16at e.g. reverse bias to the light-receiving part 16. In an instance inwhich the light-emitting part 14 is intermittently driven, the powersupply to the light-receiving part 16 is also intermittently fed, andthe AC component is also intermittently amplified. The amplificationcircuit 92 is formed on e.g. the mother board, and wiring between theamplification circuit 92 and the light-receiving part 16 is formed one.g. the substrate 41 shown in FIG. 4. The amplification circuit 92 mayalso have an amplifier for amplifying the light reception signal at astage prior to the high-pass filter. In an instance in which theamplification circuit 92 has an amplifier, the amplifier is formed e.g.on the substrate 41 shown in FIG. 4.

The A/D conversion circuit 93 shown in FIG. 9 converts an AC signalgenerated in the amplification circuit 92 into a digital signal (i.e., afirst digital signal). The acceleration detecting part 96 shown in FIG.9 calculates e.g. gravitational acceleration in three axes (i.e.,x-axis, y-axis, and z-axis) and generates an acceleration signal.Movement of the body (i.e., the arm), and therefore the movement of thebiological information measuring device, is reflected in theacceleration signal. The A/D conversion circuit 97 shown in FIG. 9converts the acceleration signal generated in the acceleration detectingpart 96 into a digital signal (i.e., a second digital signal).

The digital signal processing circuit 98 shown in FIG. 9 uses the seconddigital signal to remove or reduce the body movement component in thefirst digital signal. The digital signal processing circuit 98 may beformed by e.g. an FIR filter or another adaptive filter. The digitalsignal processing circuit 98 inputs the first digital signal and thesecond digital signal into the adaptive filter and generates a filteroutput signal in which noise has been removed or reduced.

The pulse rate computation circuit 94 shown in FIG. 9 uses e.g. fastFourier transform (or in a broader sense, discrete Fourier transform) toperform a frequency analysis on the filter output signal. The pulse ratecomputation circuit 94 identifies a frequency that represents apulsating component based on a result of the frequency analysis, andcomputationally obtains a pulse rate.

A first aspect of the illustrated embodiment relates to a biologicalinformation detector, characterized in comprising: a light-emitting partsubjected to emit a first light directed at a detection site of a testsubject and a second light directed in a direction other than adirection of the test subject; a first reflecting part subjected toreflect the second light and directing the second light towards thedetection site; a light-receiving part subjected to receive light havingbiological information, the light produced by the first light and thesecond light being reflected at the detection site; and a secondreflecting part subjected to reflect the light having biologicalinformation from the detection site and directing the light havingbiological information towards the light-receiving part.

According to the first aspect of the illustrated embodiment, the secondlight, which does not directly arrive at the detection site of the testsubject (e.g. a user), also reaches the detection site via the firstreflecting part. Therefore, the amount of light reaching the detectedpart increases, and the detection accuracy (i.e., signal-to-noise ratio)of the biological information detector improves.

According to a second aspect of the illustrated embodiment, thelight-emitting part may have: a first light-emitting surface foremitting the first light, the first light-emitting surface facing thedetection site; and a second light-emitting surface for emitting thesecond light, the second light-emitting surface being a side surface ofthe first light-emitting surface; the first reflecting part may have awall part surrounding the second light-emitting surface; and the wallpart may have a first reflecting surface for reflecting the second lighttowards the detection site.

The wall part (i.e., the first reflecting part) surrounding the secondlight-emitting surface of the light-emitting part having the firstreflecting surface thus increases the amount of light reaching thedetection site, and the accuracy of the biological information detectorfurther increases.

According to a third aspect of the illustrated embodiment, the wall partmay further have a second reflecting surface for reflecting light thathas been reflected at a surface of the test subject and does not containbiological information, thereby suppressing the light not havingbiological information from being incident on the light-receiving part.

The second reflecting surface of the first reflecting part is thuscapable of minimizing incidence of light not having biologicalinformation (i.e., invalid light) onto the light-receiving part andimprove the S/N (i.e., signal-to-noise ratio).

According to a fourth aspect of the illustrated embodiment, the firstreflecting part may project further towards the detection site than thelight-receiving part.

Specifically, the shortest distance between the first reflecting partand the surface of the test subject may be smaller than the shortestdistance between the light-emitting part and the surface of the testsubject. The first reflecting part may thus project towards thedetection site by e.g. a predetermined height Δh1 in relation to asurface of the light-emitting part that determines the shortest distancerelative to the surface of the test subject (e.g. the firstlight-emitting surface). Specifically, a spacing between the firstreflecting part and the surface of the test subject (e.g. Δh2=Δh0−Δh1)may be smaller than a spacing that represents the shortest distancebetween the light-receiving part and the surface of the test subject(e.g. Δh0=Δh1+Δh2). Therefore, in the first reflecting part, thepresence of e.g. a projection Δh1 from the light-emitting part makes itpossible to increase the area of the first reflecting surface andincrease the amount of light reaching the detection site. Also, withregards to the light reflected at the detection site, the presence ofe.g. Δh2 makes it possible to obtain a light path for the light to reachthe second reflecting part from the detection site. Also, in an instancein which the first reflecting part has the second reflecting surface,adjusting Δh1 and Δh2 allows the amount of light having biologicalinformation (i.e., valid light) and light not having biologicalinformation (i.e., invalid light: noise) incident on the light-receivingpart to be respectively adjusted, thereby making it possible to furtherimprove the S/N.

According to a fifth aspect of the illustrated embodiment, thebiological information detector may further comprise a substrate havinga first surface, and a second surface facing the first surface; whereinthe light-receiving part may be positioned on the first surface; thefirst reflecting part may be positioned on the second surface; and anequation W1≦W2 may be satisfied, when, in a cross-sectional view, W1 isa maximum value for the length of the first reflecting part in adirection parallel to the first surface, and W2 is a maximum value forthe length of the light-receiving part in the direction parallel to thefirst surface.

Having the maximum value W1 for the length of the first reflecting partbe equal to or smaller than the maximum value W2 for the length of thelight-receiving part thus makes it possible to increase the valid amountof light reaching the second reflecting part. Specifically, the maximumvalue W1 for the length of the first reflecting part may be set so thatthe first reflecting part does not block or reflect light reflected atthe detection site (i.e., reflected light having biologicalinformation).

According to a sixth aspect of the illustrated embodiment, a reflectingsurface of the second reflecting part may be a spherical surface or aparabolic surface, wherein a center of an arc defining the sphericalsurface may be within the test subject, or a focus of a parabolic linedefining the parabolic surface may be towards the test subject relativeto a light-receiving surface of the light-receiving part.

In an instance in which the detection site is within the test subject,light reflected at the surface of the test subject does not containbiological information. The inventors identified that the secondreflecting part minimizes light reflected at the surface of the testsubject (or in a broader sense, noise) in an instance in which thecenter of the arc defining the spherical surface is within the testsubject. Also, in an instance in which the reflecting surface of thesecond reflecting part is a parabolic surface, and the focus of theparabolic line defining the parabolic surface is towards the testsubject relative to the light-receiving surface of the light-receivingpart, there is a greater likelihood of light having a path that isnearly perpendicular to the surface of the test subject (e.g. thereflected first light; valid light) collecting on the light-receivingsurface of the light-receiving part.

According to a seventh aspect of the illustrated embodiment, thebiological information detector may further contain a wristband capableof attaching the biological information detector to an arm of the testsubject.

The detection site can thus be set on the arm of the test subject (i.e.,the user). In other words, the biological information detector whosedetection accuracy has been improved can be applied in an environment inwhich there is a significant level of noise arising from external light.

An eighth aspect of the illustrated embodiment relates to a biologicalinformation measuring device, characterized in comprising: thebiological information detector described above; and a biologicalinformation measuring part for measuring biological information from alight reception signal generated at the light-receiving part.

According to the eighth aspect of the illustrated embodiment, thebiological information detector whose detection accuracy has beenimproved can be used to increase the measurement accuracy of thebiological information measuring device.

Although a detailed description was made concerning the presentembodiment as stated above, persons skilled in the art should be able toeasily understand that various modifications are possible withoutsubstantially departing from the scope and effects of the presentinvention. Accordingly, all of such examples of modifications are to beincluded in the scope of the present invention. For example, termsstated at least once together with different terms having broader senseor identical sense in the specification or drawings may be replaced withthose different terms in any and all locations of the specification ordrawings.

What is claimed is:
 1. A biological information detector adapted to beattached to a user's body, comprising: a light-emitting part configuredto emit light toward the user's body; a reflecting part disposed in aperiphery of the light-emitting part to reflect at least a part of thelight emitted by the light-emitting part toward the user's body; alight-receiving part configured to receive light reflected at the user'sbody to produce a light reception signal; and a processing unitconfigured to process the light reception signal to produce biologicalinformation.
 2. The biological information detector according to claim1, wherein the reflecting part includes a reflecting surface parallel toa light-emitting surface of the light emitting part facing the user'sbody, the reflecting surface having a high reflectivity region.
 3. Thebiological information detector according to claim 2, wherein thereflecting surface has a reflectivity of 80% to 90%.
 4. The biologicalinformation detector according to claim 1, wherein the reflecting partincludes a quadrilateral-shaped region.
 5. The biological informationdetector according to claim 4, wherein a length of at least one side ofthe quadrilateral-shaped region is 100 μm to 10,000 μm.
 6. Thebiological information detector according to claim 2, wherein thereflecting surface has at least one of a curve-shaped corner and a rightangle shaped corner.
 7. The biological information detector according toclaim 2, wherein the reflecting surface has the high reflectivity regionand a low reflectivity region, and the high reflectivity region does notoverlap with the light-emitting part.
 8. The biological informationdetector according to claim 1, further comprising a protecting partconfigured to protect the reflecting part and the light-emitting part,the protecting part being made of a transparent material to transmit thelight reflected at the user's body.
 9. The biological informationdetector according to claim 8, wherein a thickness of the protectingpart is within a range from 1 μm to 1000 μm.
 10. The biologicalinformation detector according to claim 1, further comprising asubstrate physically in contact with the light-receiving part and thereflecting part and to have a thickness from 10 μm to 1000 μm.
 11. Thebiological information detector according to claim 10, furthercomprising a wiring for at least one of the light-emitting part and thelight-receiving part, the wiring being formed on the substrate.
 12. Thebiological information detector according to claim 1, further comprisingan acceleration detecting part configured to detect a movement of theuser's body and to generate an acceleration signal.
 13. The biologicalinformation detector according to claim 12, further comprising: a firstA/D conversion circuit configured to perform A/D conversion of the lightreception signal from the light-receiving part for the processing unit;a second A/D conversion circuit configured to perform A/D conversion ofthe acceleration signal from the acceleration detecting part for theprocessing unit, wherein the processing unit is configured to producethe biological information using signals from the first A/D conversioncircuit and the second A/D conversion circuit.
 14. The biologicalinformation detector according to claim 1, wherein the light-emittingpart is configured to emit the light having a maximum intensity within awavelength range of 425 nm to 625 nm.
 15. The biological informationdetector according to claim 1, wherein the light-emitting part isconfigured to emit green light.